A Chloroplast DNA Phylogeny of Solanum Section Lasiocarpa

186 SYSTEMATIC BOTANY
[Volume 29
al. (1995) in their analyses of cpDNA restriction sites
and combined cpDNA, morphological, and isozyme
data. However, their analyses of morphological and
isozyme data, alone and in combination, placed S. hirtum
within this clade, whereas this species forms an
isolated basal branch in the trn trees. Data from crossing
studies and karyotype analyses are equivocal with
respect to support for this large group (Heiser 1972,
1989; Bernardello et al. 1994).
Within this large clade, coded indel data provide
some support for the association of S. hyporhodiumwith
S. felinum. In analyses without the coded indel data, all
accessions of these two species along with S. vestissimum
form a basal grade in the large clade described
above, with S. vestissimum S432 comprising the basal
branch in the entire large clade. All three of these taxa
are high-elevation cloud forest species native to Venezuela
and northern Colombia. Whalen et al. (1981) considered
the three species to be closely related on morphological
grounds. Solanum felinum and S. vestissimum
are extremely similar morphologically, with S. hyporhodium
less so (Bruneau et al. 1995). Solanum hyporhodium
and S. vestissimum clustered together in phenetic and
cladistic analyses of isozyme data (Whalen and Caruso
1983; Bruneau et al. 1995); S. felinum was not included
in these studies. Crossing and karyotypic studies did
not support a relationship among the three taxa (Heiser
1972, 1989; Bernardello et al. 1994), although S. hyporhodium
and S. felinum had similar chromosome characteristics
(Bernardello et al. 1994). Although the three
taxa are closely associated in most of the trn trees, they
do not form a monophyletic group. In addition, the
S432 accession of S. vestissimum from Colombia is divergent
from the other four representatives of the
group, all of which are from Venezuela. Heiser (2001)
noted that accessions identied as S. vestissimum from
Colombia and Venezuela would not cross with each
other and differed in their crossing behavior with S.
quitoense. Further taxonomic work on species limits in
this complex and more intensive sampling with more
variable genes is warranted to ascertain the position of
these high altitude Colombian and Venezuelan taxa.
Two questions that have been intensively studied
with respect to this group of species concern the wild
relatives of S. quitoense and the origin and relationships
of the two Old World taxa of section Lasiocarpa. Solanum
quitoense, the lulo or naranjilla, is a commonly
cultivated fruit crop in Andean South America. Its
range has recently spread to include Central America,
where it is naturalized in Panama and Costa Rica. Solanum
quitoense has been considered by some to be
known only from cultivation, although spiny and feral
forms exist in northwestern South America. Heiser
(1972) proposed on morphological grounds that S. quitoense
is most closely related to S. candidum, but the
two species have different habitat preferences and hy-
bridize only with difculty. Although S. quitoense and
S. candidum are not sister taxa in the trn trees, there is
little character support and resolution in this area of
the tree and a close relationship between the two taxa
cannot be ruled out. However, the trn data refute hypotheses
of close associations between S. quitoense and
S. hirtum, S. pectinatum, S. stramonifolium, and S. sessiliorum.
Likewise, the relationships of the two Asian disjuncts,
S. repandum and S. lasiocarpum, have been a matter
of debate. Whalen et al. (1981) and Whalen and
Caruso (1983) suggested that S. repandum and S. lasiocarpum
were not sister taxa, but instead that S. repandum
was allied to and perhaps conspecic with S. sessiliorum,
whereas S. lasiocarpum was most closely related
to S. candidum. Conversely, Heiser considered S.
repandum and S. lasiocarpum to be closely related and
perhaps conspecic (as S. ferox) and that S. candidum
was sister to the Asian taxa (Heiser 1986, 1987, 1996).
The trn data, as well as previous data from crossing
and karytotype studies and analyses of cpDNA and
morphological characters (Heiser 1986, 1987, 1996; Bernardello
et al. 1994; Bruneau et al. 1995) supports the
close relationship between S. repandum and S. lasiocarpum
and thus Heiser’s hypothesis. Furthermore, S. candidum
emerges as a member of the S. repandum/S. lasiocarpum
clade, conforming to Heiser’s ideas of relationships.
However, S. repandum and S. lasiocarpum did
not form a monophyletic group in the trn analyses;
rather, one accession of S. repandum formed a clade
with the two S. pseudolulo accesssions. This result
should not be over-interpreted, however, since there is
little character support for the identication of lineages
within the large clade that includes S. repandum, S. lasiocarpum,
S. pseudolulo, S. candidum, S. quitoense, S. hyporhodium,
S. vestissimum, and S. felinum.
In general, the trn trees are quite similar to those
obtained from analyses of cpDNA restriction site data
(cf. Fig. 1 in Bruneau et al. 1995). This is not surprising,
given that the chloroplast genome is a single linked
non-recombining genetic entity (Doyle 1992). Further
molecular studies are underway using more variable
nuclear genes in order to achieve better resolution of
phylogenetic relationships among the species of section
Lasiocarpa, to increase support for previously identied
clades, and to compare phylogenies derived
from maternally inherited chloroplast genes with those
based on biparentally inherited nuclear markers.
ACKNOWLEDGMENTS. I thank C. Heiser, A. Bruneau, J. Miller,
P. Diggle, R. Olmstead, L. D. Gómez, and the Botanic Garden at
the University of Nijmegen, The Netherlands, for providing seed
and DNA samples; B. Hammel and R. Aguilar for eld assistance;
R. Dirig for information regarding vouchers at BH; C. Heiser, A.
Bruneau, E. E. Dickson, J. Miller, P. Diggle, S. Knapp, and D. Spooner
for comments on the manuscript and help with sample and
voucher information; M. Johnson, A. Freeman, S. King-Jones, A.
Egan, A. Moore, and K. Klatt for laboratory assistance; and C.